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John Dalton's Theory
John Dalton came up with the theory that elements consited of atoms and compounds are specific colections of atoms. This theory was for describing the composition of compounds. His theory did not explain what atoms were made of and what they were like.
Image url: http://commons.wikimedia.org/wiki/File:John_Dalton_by_Charles_Turner.jpg -
J. J. Thomson's Experiment
He was experimenting with Cathode Ray Tubes when he Discovered he could get any element to emit negatively charged particles. He concluded that these were part of an atom and because atoms are neutrally charged that there must also be a positively charged part of an atom. He called the negatively charged particles electrons.
Image url: http://en.wikipedia.org/wiki/J._J._Thomson#mediaviewer/File:J.J_Thomson.jpg -
Plum Pudding Model
Willian Thomson Came up with the theory that the atom was like plum pudding. The electrons were raisins scattered about in a positively charged cloud and that the electrons couteracted the positive cloud so that it had a neutral charge.
Image url: http://en.wikipedia.org/wiki/Plum_pudding_model#mediaviewer/File:Plum_pudding_model.svg -
Einstein Solid
Eisntsein came up with the theory that all atoms oscillate independantly but on the same frequency. This theory explained many things such as a solution the specific heat problem.
Image url: http://en.wikipedia.org/wiki/Albert_Einstein#mediaviewer/File:Einstein_1921_by_F_Schmutzer_-_restoration.jpg -
Gold Foil Experiment
He fired alpha particles at a thin gold foil and discovered that they sometimes bounced back at weird angles. This led to his theory of the nuclear atom. His theory described an atom with a charged nucleaus in the middle which was orbited by electrons.
Image url: http://en.wikipedia.org/wiki/Rutherford_model#mediaviewer/File:Rutherford_atomic_planetary_model.svg -
Oil Drop Experiment
Robert Millikan's experiment known as the oil drop experiment found the charge of an electron. J. J. Thomson found the chrge to mass ratio of the elctron so this experiment also found the mass of the electron as well.
Image url: http://en.wikipedia.org/wiki/Robert_Andrews_Millikan#mediaviewer/File:Millikan%E2%80%99s_oil-drop_apparatus_1.jpg -
Bohr Model
Neils Bohr came up with a new model of the atom in 1913. This model was a planetary one like Rutherfords but his had different energy levels for electrons, and that electrons could change levels. His theory also stated that atoms chemical properties where based off of the number of atoms in the outer energy level.
Image url: http://langlopress.net/homeeducation/resources/science/content/support/illustrations/Bohr%20Atoms/Deuterium%20Atom.jpg -
Erwin Shroedinger's Experiment
In 1922 he analyzed the electron orbits in an atom from a geometric point of view, using methods developed by the mathematician Hermann Weyl . He discovered that quantum orbits are associated with certain geometric properties, this was an important step in predicting some of the features of wave mechanics which he would later discover.
Image url: http://en.wikipedia.org/wiki/Erwin_Schr%C3%B6dinger#mediaviewer/File:Erwin_Schr%C3%B6dinger.jpg
